The present invention relates to database systems. More particularly, the present invention pertains to an apparatus and method for transforming data in data warehousing applications.
Due to the increased amounts of data being stored and processed today, operational databases are constructed, categorized, and formatted in a manner conducive for maximum throughput, access time, and storage capacity. Unfortunately, the raw data found in these operational databases often exist as rows and columns of numbers and code which appears bewildering and incomprehensible to business analysts and decision makers. Furthermore, the scope and vastness of the raw data stored in modern databases renders it harder to analyze. Hence, applications were developed in an effort to help interpret, analyze, and compile the data so that it may be readily and easily understood by a business analyst. This is accomplished by mapping, sorting, and summarizing the raw data before it is presented for display. Thereby, individuals can now interpret the data and make key decisions based thereon.
Extracting raw data from one or more operational databases and transforming it into useful information is the function of data xe2x80x9cwarehousesxe2x80x9d and data xe2x80x9cmarts.xe2x80x9d In data warehouses and data marts, the data is structured to satisfy decision support roles rather than operational needs. Before the data is loaded into the data warehouse or data mart, the corresponding source data from an operational database is filtered to remove extraneous and erroneous records; cryptic and conflicting codes are resolved; raw data is translated into something more meaningful; and summary data that is useful for decision support, trend analysis or other end-user needs is pre-calculated. In the end, the data warehouse is comprised of an analytical database containing data useful for decision support. A data mart is similar to a data warehouse, except that it contains a subset of corporate data for a single aspect of business, such as finance, sales, inventory, or human resources. With data warehouses and data marts, useful information is retained at the disposal of the decision makers.
One major difficulty associated with implementing data warehouses and data marts relates to that of data transformation. A data transformation basically includes a sequence of operations that transform a set of input data into a set of output data. As a simple example, the total sum of revenues of all of the divisions of a company minus its operating costs and losses will result in the profit for that company. In this example, revenue for each division, company operating costs, and company losses are input data and the company profit is the output data, while the transformation is basically comprised of simple arithmetic operations. This example could become much more complex for a large company that offers numerous products and services in various regions and international markets. In such a case, the transformation is no longer a simple arithmetic formula, but becomes a complex network of data transformations (e.g., SQL-Structured Query Language expressions, arithmetic operations, and procedural functions) that define the process for how the input data from various sources flow into the desired results in one or more target databases.
Presently, the existing approaches for handling transformations for data warehousing applications can be classified into three categories: using procedural programming languages (e.g., C, C++, and COBOL); using SQL expressions; or a combination of these two. Any of these three approaches, however, is primarily focused on capturing the low-level algorithmic behavior of transformations and does not by any means facilitate the definition and exchange of transformation metadata (i.e., data that describes how data is defined, organized, or processed). Furthermore, this was usually performed by a highly specialized software engineer who would design custom programs tailored to specific applications. Such programmers are relatively scarce and are in high demand. As such, even a simple task can be quite expensive. More complex data transformations are extremely costly to implement and time-consuming as well, especially given that most data transformations involve voluminous amounts of data that are viewed and interpreted differently by various analysts and decision-makers. In today""s highly competitive marketplace, it is often crucial that the most recent information be made available to key individuals so that they can render informed decisions as promptly as possible.
Moreover, software vendors in the data warehousing domain often offer specialized tools for defining and storing transformation information in their products. Such tools are still geared towards algorithmic behavior of transformations and usually provide graphical user interfaces to facilitate the use of procedural languages and/or SQL for that purpose. Bur more significantly, the format in which such transformation information is represented and saved is system-specific and low-level such that exchanging this information with other similar software becomes extremely difficult and error-prone. Hence, data transformation software might work properly for one database, but might be incompatible with another database which contains critical data. Presently, the only high-level protocol used for describing and exchanging transformation information between different data warehousing software is limited to the definition of field-level transformations with SQL statements that include logical, arithmetic, and string operations.
Thus, there exists a strong need in the data warehousing industry for some formal mechanism for exchanging metadata as well as the need for a computer-parsable language that could concisely describe various characteristics of complex data transformation networks. The present invention offers a solution with the conception and creation of a Transformation Definition Language (TDL).
The present invention pertains to a transformation description language (TDL) used for specifying how data is to be manipulated in a data warehousing application. The TDL is comprised of one or more sources for storing raw data, one or more transformation objects for processing the raw data according to predefined instructions, and one or more targets for storing the processed data. A mapping is used for directing the data flow between the I/O ports corresponding to the sources, the plurality of transformation objects, and the targets. The mapping specifies the connectivity between the sources, transformation, and target objects as well as the order of these connections. There are a number of different transformations which can be performed to manipulate the data. Some such transformations include: an aggregator transformation, an expression transformation, a filter transformation, a lookup transformation, a query transformation, a sequence transformation, a stored procedure transformation, and an update strategy transformation.